The invention concerns an advisory lighting fitting with a luminous body, in particular an emergency sign light.
Advisory lighting fittings familiar from the state of the art consist of a luminous body, which has a light-radiating light outlet surface, which is divided up into part surfaces radiating in various colours. Here the part surfaces in one colour are defined, for example, by means of pictogram elements or advisory elements, while the part surfaces or part surface in the other colour form the background or frame for the advisory elements. Usually, light is radiated into the luminous body from at least one light source, the light being reflected on the limiting surfaces of the luminous body and then emitted via the light outlet surface. The luminous body may consist of one or more transparent, flat light-conducting bodies exploiting the lighting effect, in whose side edges light is stored and from the surface of which light is deflected through arrangements interrupting the total reflection. In another embodiment of the state of the art, the luminous body consists of a flat hollow-body with translucent light-radiating covers towards at least one side, often towards the two opposite sides also. In the hollow space either lamps and reflectors are arranged to provide rear lighting for the advisory elements or light is radiated in a light pocket via at least one longitudinal side of the luminous body.
According to the international standard, the advisory lighting fittings are usually characterised by a green and a white radiating surface. According to the state of the art, the colour of light of the white-radiating surface parts is acquired from the colour of light of the light source, such as the fluorescent lamp, electric light bulb or light-radiating diode, or rather the LED combination, while the coloured portion of the advisory lighting fitting, the green colour in the case of emergency signs, is acquired through spectral filtering of the white light. The luminous flux requirement of the sign is therefore calculated from the luminous flux requirement of the white surface because this is used according to the state of the art to provide rear lighting for the coloured surface parts.
For emergency signs, an average luminance of 200 cd/m2 of the light-radiating pictogram surface is required for mains operation in a bright environment according to the German standard DIN 4844, this with a white/green illuminance contrast  greater than 5:1 and a green surface content of at least 50%. With a normal surface content of white colour of 33%, a luminance of the white surface of 425 cd/m2 is produced in order to meet the requirement of an average luminance of 200 cd/m2.
For a single-sided radiating surface of 150 mmxc3x97300 mm, at diffuse light radiation, from the above luminances a luminous flux requirement of light radiation of 60 lm with a luminance of 425 cd/m2 is produced according to this calculation.
Under conditions of emergency operation, the required luminance will be considerably reduced. Thus a minimum luminance of 5 cd/m2 is required for the green-radiating surfaces. Because of the illuminance contrast requirement, a minimum luminance of 25 cd/m2 will therefore result for the white surfaces. This means when converted that the luminous flux required for the emergency operation can be reduced by a factor 19 vis-xc3xa1-vis the mains operation.
To satisfy the requirements when using light-emitting diodes as a light source, which usually have a very much longer service life than electric light bulbs and normal fluorescent lamps, an electric rating of 20 to 24 W ought to be installed in a bright environment, given a typical luminous efficiency of 10 lm/W, and for emergency operation 1 to 1.2 W specific to a double-sided radiating sign of the size 150xc3x97300 mm. However, not only is this no longer an economic use of energy, but also more than 300 light-emitting diodes are needed to meet the requirements given a specific output of typically 0.05 to 0.1 W per diode. Even with a sought-after output of 0.2 W per diode, 115 light-emitting diodes are still needed. This leads to uneconomically high manufacturing costs. Similar considerations apply to other colour combinations, too.
With the use of conventional lighting, especially fluorescent lamps with normal diameters of 16 mm, poor light output ratios may have to be accepted due to the high luminous efficiency. With the use of light-emitting diodes, the light output ratio again plays a fundamental role in the economic efficiency. The light output ratio of a colourfully radiating luminous body results, on the one hand, from the losses in the production of the coloured light, while, on the other hand, with punctiform light sources such as light-emitting diodes, further losses result from the conversion of the luminous density distribution in all-over radiating light outlet surfaces.
The aim of the invention therefore is to create an advisory lighting fitting with a luminous body which has at least one light outlet surface, which is divided up into coloured or multi-coloured radiating part surfaces, where the desired luminances of the light-radiating surfaces can be manufactured with a power requirement which is considerably reduced compared with that of the state of the art.
Because the luminous body of the advisory lighting fitting is composed of light conducting plates or hollow bodies arranged above, next to and in each other and having various part surfaces, and because various light sources are assigned to the light conducting plates or hollow bodies corresponding to the part surfaces radiating in various colours, which light surfaces radiate variously coloured light into the respective light conducting plates or hollow bodies, the colour production may be avoided via filtering and the correspondingly greater luminous efficiency of the coloured light sources in the form of one or more light-emitting diodes or coloured fluorescent lamps becomes fully effective.
Through the arrangements specified in the subclaims, advantageous further developments and improvements are possible. It is particularly advantageous that a filter is arranged in front of at least one part surface, which filter has a spectral transmission, which is as great as possible in the wavelength range of the light radiated by the assigned light source and which, when radiated with an external light of another colour, for example white, essentially retains the colour of the supplying light-sources or the radiating surface.
It is also particularly advantageous that the light-radiating surfaces of the light sources and the light entry surfaces of the limiting walls of the luminous body or light conducting plates or hollow bodies are adapted to each other in such a way that essentially the entire radiated light from the light sources reaches the luminous body and that the remaining limiting surfaces, which face the interior of the luminous body, have great reflectivity.